Vue Patch Flags: Optimizing Re-renders with Fine-Grained Updates

Modern JavaScript frameworks like Vue leverage virtual DOM and efficient patching mechanisms to minimize DOM manipulations, leading to better performance. A key technique for achieving this efficiency is the use of "patch flags." This challenge asks you to implement a simplified version of Vue's patch flags to understand how they help identify specific types of DOM updates.

Problem Description

Your task is to create a system that can generate and interpret "patch flags" for virtual DOM nodes in a Vue-like rendering process. These flags are integer values that encode information about the type of updates required for a specific DOM element. By using these flags, the rendering engine can avoid unnecessary re-renders and directly target the parts of the DOM that have changed.

You will need to:

1. Define a set of patch flag constants: These constants will represent different types of DOM updates (e.g., text changes, attribute changes, event listener updates, class/style changes).
2. Create a function to generate patch flags: This function will take a virtual node and its updated version as input and return an integer representing the combined patch flags for that node.
3. Create a function to interpret patch flags: This function will take a patch flag integer and return an array of human-readable strings describing the types of updates indicated by the flags.

Key Requirements:

• Bitwise Operations: Patch flags should be implemented using bitwise operations, where each flag corresponds to a unique bit position.
• Combinable Flags: Multiple flags for a single node should be combinable using the bitwise OR operator.
• Clear Human-Readable Output: The interpretation function should provide easily understandable descriptions of the flags.

Expected Behavior:

• If a node has no changes, its patch flag should be 0.
• If a node has multiple types of changes, its patch flag should be the result of OR-ing the individual flags.
• The interpretation function should correctly identify all active flags within a given integer.

Edge Cases:

• Nodes with no children or only text content.
• Nodes with only attribute changes.
• Nodes with both attribute and text changes.

Examples

Example 1:

Input:
- Original Node: { type: 'div', props: { id: 'my-div' }, children: 'Hello' }
- Updated Node:  { type: 'div', props: { id: 'my-div', class: 'active' }, children: 'Hello World' }

Output:
Patch Flags Integer: 9 (e.g., 1 (TEXT) | 8 (CLASS))
Readable Flags: ['TEXT', 'CLASS']

Explanation: The 'children' (text content) has changed, and a 'class' attribute has been added. We assume 'TEXT' flag is 1 and 'CLASS' flag is 8.

Example 2:

Input:
- Original Node: { type: 'button', props: { onClick: () => {} }, children: 'Click Me' }
- Updated Node:  { type: 'button', props: { onClick: () => console.log('Clicked!') }, children: 'Click Me' }

Output:
Patch Flags Integer: 4 (e.g., 4 (PROPS))
Readable Flags: ['PROPS']

Explanation: The 'props' (specifically an event listener) has changed. We assume 'PROPS' flag is 4.

Example 3: (Edge Case)

Input:
- Original Node: { type: 'span', props: {}, children: 'Static Text' }
- Updated Node:  { type: 'span', props: {}, children: 'Static Text' }

Output:
Patch Flags Integer: 0
Readable Flags: []

Explanation: There are no changes to the node.

Constraints

• The maximum number of distinct patch flag types will not exceed 32 (to fit within a standard 32-bit integer).
• Input virtual nodes will be represented as simple JavaScript objects with type, props, and children properties. children can be a string or an array of other virtual nodes. props is an object of key-value pairs.
• Performance is not a primary concern for this challenge; clarity and correctness of the flag generation and interpretation are paramount.

Notes

• Think about common DOM update scenarios and how they can be represented efficiently.
• You'll need to define your own constants for the patch flags. Assign them powers of 2 (1, 2, 4, 8, 16, ...) to ensure they can be combined using bitwise OR without conflicts.
• The interpretation function will likely involve checking individual bits of the flag integer.